Image via WikipediaThere's the muscle sheaths that have stiffened by the lack of use of the full range of motion and the constant deposition of collagen, which literally glues the sheath to itself. This tight sheath can impair blood flow to a muscle, especially when the muscle is contracted for a long time. The contracting muscle presses out against a tight sheath. Blood takes the path of least resistance.
That lack of healthy blood flow can cause the sarcomeres, the contractile unit of muscle, to get stuck in their contracted position. This is how a muscle gets tight and actually shorter.
When a muscle gets very stiff, a trigger point can develop. A trigger point is just an area where many sarcomeres are tight. We certainly notice trigger points, but the muscle gradually hardens for a while before a trigger point develops.
The hard muscles are shorter and thicker and this makes manipulating the sheath to break up the collagen much harder. But if the muscle is softened first, it can be done.
Massage is how you soften the muscle and get the sarcomeres in it functioning again. Massage pushes depleted blood out and then new blood is pulled in from the capillaries.
But there's still one other factor and that is the way muscles communicate with each other to accomplish work. When one muscle is engaged, other muscles receive nerve signals to help. And if there is a trigger point in one muscle, other muscles are engaged via the nerves.
When trying to sit for a long time, tight muscles may be pulling you in one direction, requiring other muscles to have to work constantly to keep you upright. This is why maintaining a natural posture can be difficult. It ought to be something you don't have to struggle to do.
So you may have a tense muscles but it may be another muscle that is the root cause. All of the muscles need to considered and massaged in a systematic way.
